Field of the Invention
The present invention relates to: a power transmission unit in which a driving unit including a rotary member forwardly or reversely rotated by a drive device is removably mounted with a driven unit including a rotated member to be connected to the rotary member and which is adapted to enable a one-way clutch to transmit the forward rotation of the rotary member to the rotated member or to disable the one-way clutch to transmit the reverse rotation of the rotary member to the rotated member; an image forming apparatus employing such a power transmission unit; a control method for such a power transmission unit; and a computer-readable medium carrying a control program for such a power transmission unit.
Description of the Related Art
The image forming apparatuses such as copiers, printers, facsimiles and multi-functional peripherals thereof have conventionally employed a power transmission unit in which the rotary member rotatably driven by the drive device disposed at the driving unit of a main body of the apparatus is connected with the rotated member such as a toner bottle or photoreceptor drum disposed in the driven unit such as a toner cartridge or process cartridge so as to transmit the rotation of the rotary member to the rotated member.
Such a power transmission unit where the rotary member is connected with the rotated member so as to transmit the rotation of the rotary member to the rotated member is disclosed in Patent Document 1 (Japanese Unexamined Patent Publication No. 2010-169875) and the like. The power transmission unit is constructed as follows. One of the connecting members interconnecting the rotary member and the rotated member is circumferentially formed with a plurality of engaging claws projected toward the other connecting member while the other connecting member is circumferentially formed with a plurality of engageable grooves to be engaged with the engaging claws. The driven unit is mounted to the driving unit. The one connecting member connecting the rotary member to the rotated member is biased to the other connecting member by a biasing member such as a spring so as to bring the engaging claws formed at the one connecting member into engagement with the engageable grooves formed at the other connecting member.
According to such a power transmission unit, with the engaging claws of the connecting member engaged with the engageable grooves of the other connecting member, the rotary member is rotated by the drive device while the one-way clutch is enabled to transmit the forward rotation of the rotary member to the rotated member but is disabled to transmit the reverse rotation of the rotary member to the rotated member.
In the above-described power transmission unit, however, all the engaging claws of the one connecting member are not always brought into proper engagement with all the engageable grooves of the other connecting member when the driven unit is mounted to the driving unit.
In a state where all the engaging claws are not properly engaged with all the engageable grooves, for example, the forward rotation of the rotary member, which is forwardly rotated by the drive device, cannot be adequately transmitted to the rotated member via the connecting members so that the rotated member cannot be rotated properly. There is another problem that even though only some of the engaging claws engage with the engageable grooves, load is applied between the some engaging claws and engageable grooves in engagement, causing damage on these engaged parts.
Therefore, Patent Document 1 proposes the following procedure. After the driven unit is mounted to the driving unit, the drive device reversely rotates the rotary member before forwardly rotating the rotary member. Thus, frictional force between the engaging claws and the engageable grooves is reduced in case that the engaging claws are shallow-engaged with the engageable grooves. This allows the engaging claws to be properly engaged with the engageable grooves.
In the above-described power transmission unit, however, the one-way clutch merely transmits the forward rotation of the rotary member to the rotated member via the connecting members. When the rotary member is reversely rotated, therefore, the connecting member disposed at the rotary member is not rotated but the rotary member idles alone.
If the rotary member is reversely rotated with the above-described engaging claws and engageable grooves totally out of engagement, the rotary member idles alone while the connecting member disposed at the rotary member is not rotated. Hence, the engaging claws formed at the connecting member of the rotary member do not come into engagement with the engageable grooves formed at the connecting member of the rotated member.
In a case where the rotary member is forwardly rotated with the engaging claws and the engageable grooves totally out of engagement as just described, all the engaging claws are not always engaged with all the engageable grooves, as described above. Only some of the engaging claws engage with the engageable grooves while the other engaging claws run on the other connecting member, failing to engage with the corresponding engageable grooves. When the rotary member is forwardly rotated in this state, the forward rotation of the rotary member is not adequately transmitted to the rotated member. There still exists the problem that the rotated member is not rotated properly or that the load is applied between the some engaging claws and engageable grooves, causing damage on these components.